Apparatus for manufacturing sheet-cutting female dies

ABSTRACT

A compact apparatus for use in the manufacture of sheet-cutting female dies includes a cabinet having an assembly of melting and casting pots with associated heating and progressive cooling means governed by an electrical control system. A method for manufacturing the die in a comparatively short time as contrasted with conventional machining methods, is disclosed.

[ Sept. 4, 1973 FOREIGN PATENTS OR APPLICATIONS 698,303 10/1953 GreatBritain.. 164/126 Primary Examiner.l. Spencer Overholser AssistantExaminer-John E. Roethel Att0meyWilliam E. Sherwood I r i 111 ill SatesI atent [191 Shelton et a1.

APPARATUS FOR MANUFACTURING SHEET-CUTTING FEMALE DIES Inventors: WinstonL. Shelton, Jeffersontown;

Joseph L. Newman, Louisville, both of Ky.

Assignees Quik-Die, Inc., Jeffersontown, Ky.

Apr. 14, 1971 App]. No.: 133,853

22 Filed:

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3 Claims, 7 Drawing Figures electrical control system. A method formanufacturing the die in a comparatively short time as contrasted withconventional machining methods, is disclosed.

[56] References Cited UNITED STATES PATENTS rmmeustrma u 1 g 3356308 9 Bn S INVENTORS WINSTON Lv SHELTON ATTORNEY JOSEPH L. NEWMAN W. E Haw/HQFATENTEDSEP Mm 3.756308 SHEET 2 0F 3 FIG. 4

l2 1 JOSEPH L. NEWMAN "5y wzsiwxi ATTORNEY co m INVENTORS WINSTON L.SHELTON I JOSEPH L. NEWMAN SHEET 3 [IF 3 PATENTEB m 4 ms ATTORNEYAPPARATUS FOR MANUFACTURING SHEET-CUTTING FEMALE DIES BACKGROUND OF THEINVENTION The manufacture of high-quality female dies to be usedwith apunch, or male dies, in a press for forming apertures in sheet material,has long been recognized as a time consuming and expensive procedure.When such die is to be made by machining techniques involving drillingand inside cuts many hours of time by an expert machinist may berequired. Also, when the female die is to be cast and then allowed tocool with proper crystal growth and with accurate dimensions of thefinished die, exacting supervisory demands are placed upon the operatorwho performs the casting step and controls the rate of cooling. Not onlymust a highly skilled operator be employed, but also a need exists forappropriate, labor-saving apparatus which that operator may employ inthe die manufacturing process.

It is, therefore, a purpose of the present invention to employ a methodand apparatus which will overcome disadvantages of the above describednature as presently found in the die manufacturing art.

SUMMARY Apparatus used in accordance with the invention comprises acasting pot or mold, with its side selectively heated by upper and lowerresistance heaters and with its bottom exposed to a controlled source ofcooling air. A detachable die plate definingthe upper face of the castdie is positioned in the casting pot and holds a male die in contactwith the bottom of the pot, and around which male die the melt is pouredthrough apertures at the periphery of the die plate. A selectivelyoperable blower directs a stream of cooling air against the bottom ofthe pot to cause the melt in the pot to solidify progressively outwardfrom the male die, and a timer controlled system deactivates the firstand second heaters in sequence to cause the melt to solidifyprogressively upward from the bottom of the pot.

Preferably, the apparatus includes a cabinet supporting the casting potand an adjacent melting pot together with an electrical systemcontrolling the heat employed in both the melting and casting steps.

The method of the invention includes the positioning of the male die,with which the cast female die will later cooperate in a sheet-cuttingpress, within a mold space, and the subsequent casting of the female diein that space. The progressivesolidification of the hot female die isconducted in the presence of a supply of residual flowable melt so thatcontraction of the solidifying melt material is compensated by continuedintroduction of flowable melt into the mold space. Following theformation of the female die, the two dies are removed form the castingapparatus and are then separated from each other. I

Among the objects of the invention are the provision of an improvedmethod of forming female sheet-cutting dies in a rapid and economicalmanner; the provision of an improved method for selectively controllingthe solidification and crystallization of a metallic female die duringits casting; the provision of an improved apparatus for casting femaledies; the provision of a compact apparatus having a melting pot and acasting pot located conveniently near each other and with readilyaccessible controls for operating the melting and casting operations;and the provision of an improved electrical control system for governingthe heating of a melting pot and of an adjacent casting pot mounted in acabinet containing the control system.

These and other objects and advantages of the invention will become moreapparent as the description proceeds and when considered in conjunctionwith the accompanying drawings in which:

FIG. 1 is a perspective view of the cabinet with the pot cover removed.

FIG. 2 is a sectional view of the upper portion of the cabinet taken online 2--2 of FIG. 1.

FIG. 3 is a sectional view of the melting pot taken on line 3-3 of FIG.1 and with the cover in place.

FIG. 4 is a plan view of a portion of the cabinet top with the die plateinstalled in the casting pot.

FIG. 5 is a schematic diagram of the electrical circuitry of theapparatus.

FIG. 6 is a perspective view of the melting pot bushing with the heatersin place, and

FIG. 7 is a top plan view of the pot shown in FIG. 6.

Referring first to FIG. 1, a compact cabinet preferably provided withcasters 10 for portability, comprises a main housing having side wallsl1, 12 to which is attached an apertured cover 13 at a convenientworking height. An interior horizontal shelf 14 attached to the sidewalls and to a rear wall 15 provides a support for the pots and otherelements later to be described. Hinged doors 16, 17 at the front of thecabinet provide access to the interior and at the rear a manifold 18attached to the rear wall and extending to the sides of the cabinetserves to exhaust hot air entering that manifold from conduit 19supported by the shelf. A supplementary housing for certain electricalcontrol units includes a mounting plate 20 attached to the cover plate13 and to the rear wall 15, and has a vertically extending portion 21merging into an inclined panel portion 22 and thence into a top panelportion 23. This supplementary housing serves as a backsplash the rearof which preferably is open, and which is defined by end portions, oneof which is shown at 24.

Passing now to FIGS. 3, 6 and 7, a metallic pot 30, formed of a metalwhich will withstand high temperatures and without alloying with themelt material employed, preferably is of circular cross section and fitswith a small clearance into a stationary metallic tubular bushing 31having resistance heaters, later to be described, attached to its outerperiphery. Surrounding these heaters is a tube 32 of heat insulatingmaterial supported upon shelf 14; a disc 33 of similar insulatingmaterial being interposed between the shelf and the bottoms of pot 30and of the bushing 31. In addition, an apertured slab 34 of similarinsulating material rests upon the tube 32 in surrounding relation tothe bushing 31. Space between the heating coils and the tube ofinsulation may conveniently be packed with loose insulation 35.

The top edge of the melting pot is formed with apertures 36 arrangedabove the top edge of the bushing and through which a manually operabletool 37 may be detachably secured for use in lifting and transporting:the melting pot and its. contents during the practice of the methodsteps of the invention. Various forms and arrangements of heaters may beemployed, but we prefer to use a heater such as the Chromalox typeI-IBT-SO available from Edwin L. Wregand Co., Pittsburgh, Pa. andarranged as indicated in FIGS. 6 and 7. As shown therein, a pair ofU-shaped heaters 38, 39 bent into arcuate form corresponding to theouter periphery of the bushing 31 forms the heat source for the uppersection of the melting pot and are connected at one terminal by ahorizontal bar to which conductor 115 extends. A pair of similar heaters41, 42 forms the heat source for the lower section of the melting potand are connected at one terminal by a horizontal bar 43 to whichconductor 119 extends. Vertical bars 44, 45 connect the other terminalsof heaters 38 and 41 and of heaters 39 and 42, respectively.

As shown in FIG. 2, a tubular sleeve having an internally disposedhorizontal plate 51 with a central aperture therein is attached to theupper side of shelf 14 and has a side aperture through which the conduit19 extends. Supported upon the plate 51 is the end of a tubular wall ofcasting pot or mold 52 which in conjunction with a bottom portion 53forms a mold space. This pot 52 and its bottom 53 are formed of a metalwhich will withstand high temperature and without alloying with the meltmaterial. Significantly, the lower surface of the bottom 53 is indentedto assume greater heat transfer surface while the upper surface of thebottom portion is smooth. Altemately, heat radiating fins may beattached to the central part of bottom 53 to provide a heat sump.Immediately below the casting pot a substantial space 54 is provided andinto which space a nozzle 55 from a blower casing 56 is directed. Thiscasing is supported from the lower face of shelf 14 and includes anintake 57 communicating with the interior of the cabinet. The casingalso houses an impeller driven by a motor 58. Relatively cold airemerging from nozzle 55 abstracts heat from the bottom of the pot nearthe center of the pot to assist in the progressive cooling of the castfemale die from its center outwardly, and the thus heated air then isvented into the manifold by means of conduit 19.

Attached to the outer face of pot 52 are a plurality of heaters of thetype employed with the melting pot, but arranged as indicated in FIG. 5.In this arrangement the heaters 59, 60 at the lower portion of the pothave one terminal thereof connected to a bar 61 to which conductor 121extends, whereas the other terminal thereof is connected to a bar 62 towhich conductor 114 extends. The heaters 63, 64 at the upper portion ofpot 52 have one terminal connected by bar 65 to which the conductor 114also extends. One other terminal of heaters 63, 64 is connected to a bar66 to which conductor 117 extends. Accordingly, as will later appear,both the upper and lower sections of the casting pot may be heatedsimultaneously in preparation for the casting step and thereafter theupper section may continue to be heated while the lower section iscooling and effecting a progressive solidification of the cast femaledie from the bottom upwardly.

Disposed within the sleeve 50 is a tube 70 of heat insulating materialand with the space between this tube and the heaters being filled withloose insulation 71. The slab 34 of heat insulating material whichsurrounds the melting pot also surrounds the casting pot and is disposedabove the heaters 63, 64. The upper end of the casting pot wall extendsabove the top 13 of the cabinet and is provided with diametricallyopposed slots 72, 73 (FIG. 1) into which a pull bar 74 may beselectively engaged or disengaged.

As a significant feature, a die plate, or mold cover, 75 udjustablyaffixed to the pull bar and adapted for insertion into the casting potwith a small clearance, for example about 0.01 inch, is formed with oneor more, and preferably four symmetrically spaced, cut-away portions 76at its periphery. The upper surface of this die plate also is inclineddownwardly toward the periphery of the plate as indicated at 77. Whenthis die plate is installed in the casting pot and heat is being appliedby the heaters, a manually adjustable cover for the pots as indicated inFIGS. 2 and 4 may be used to retain heat and to shield the operator.Such a cover includes a handle 78 attached to a casing 79 having adownwardly directed wall which rests upon a suitable sheet 80 ofprotective material for preventing damage to the slab 34 of insulation.On the interior of this cover a slab 81 of heat insulating material issecured thus to confine heat being radiated from the described pots.

The method steps of the invention include not only the automaticallycontrolled cooling of the female die cast in pot 52 but also the stepspreparatory to such casting as now to be described. Accordingly, themale die or punch 82, with which the female die will later be used in apress, is first positioned upon the bottom plate 53 of the mold and thedie plate 75 is clamped thereagainst with the pull bar 74 locked in theslots 72, 73. The male die will be formed of a metal, such as steel,having a smaller coefficient of expansion than the metal, such as azinc-based alloy, comprising the female die.

Assuming the melting pot 30 to contain the requisite amount of moltenmetal at a suitable temperature for example about 800 F.; the castingpot 52 to be heated to the appropriate temperature, for example about820 F.; and the circuits to the heaters and the blower to beinterrupted, the operator is ready to proceed with the casting step. Pot30 and its melt are lifted by means of tool 37 and tipped to pour theflowable melt upon the inclined surface of die plate 75 whereupon themelt flows through the cutaway portions 76 and fills the space belowthat die plate as indicated by the stippled body 83. Sufficient flowablemelt is present at this time to form a reservoir above the plate asindicated by the strippled sprues 84, 85 (FIG. 2). Having thus made thepour the operator restores the melting pot to normal position and thensets the timer Referring to FIG. 5 showing a preferred form of circuitryfor the electrical elements of the described appa- ,ratus, certaincircuits are indicated in dotted lines to show the optional use of a 240volt power source.

50 Mounted upon the panel portion 22 of the cabinet is a manuallyoperable main switch 100, an adjustable timer 101 (which convenientlymay be the Cramer Type 27lA-2-60 timer available from Conrac Corp., OldSaybrook, Conn.) and a pair of controllers 102 and 55 103 (whichconveniently may be the Fenwal Model 524 available from Walter KiddieCo., Ashland, Mass.) for the melting and casting pots respectively. Aswill be understood, these controllers include internal switches 104, 105respectively, whose positions are controlled 60 by the manual setting ofthe controllers to a predetermined maximum heating of the pots, and bytemperature sensing probes 106, 107 mounted in those pots and connectedto the controllers by conductors 108, 109. Conventional relays 110, 111and 112 incorporated in 65 the circuit may conveniently be mounted onthe plate 20 of the cabinet as seen in FIG. 2.

In initiating a typical operation as partially described above, theoperator after having loaded the melting pot with melt material andhaving secured the male die and die plate in the casting pot, and havingset the controllers 102 and 103 to a desired heat reading, then closesthe main switch 100 which energizes relay 110 as long as that switch isclosed. Preferably the cover is in place over the pots at this time. Asswitch 100 closes, a circuit is made energizing relay 110 and since thecontroller switches 104, 105 are now set to their solid line positions,relays 111 and 112 also are energized. Through conductors 113, 114, 121,relay 111 and conductor 116, the lower heater in the casting pot is nowenergized; and through conductors 117, 118 and relay 111 the upperheater in the casting pot is likewise energized. Also, throughconductors 115, 119, relay 112, conductor 120 and relay 111, bothheaters in the melting pot are energized. At this time, of course, thetimer 101 and blower motor 58 are deenergized.

During the heating period which may, for example, be about one hour, theoperator may perform other duties while occasionally noting the dials ofthe controllers. When, therefore, the probes 106and 107 indicate thatthe appropriate temperatures have been reached, the operator returns thecontrollers to their zero readings causing switches 104 and 105 to moveto their dotted line positions and deenergizing relays 112 and 111. Thecover is then removed and the abovedescribed pour of the melt into thecasting pot then is made, and thereafter the timer 101 is set to aselected time, for example one hour, and is energized by closing thetimer'switch. As this occurs the internal cams of the timer cause blade130 to move into contact with terminal 131 and to establish a circuitthrough conductors 132, 133, blade 130, contact 131, conductors 134, 117, upper heaters 63, 64 of the casting pot, and conductors 114 and 113.

At the same time the timer blade 135 is moved into contact with terminal136 and a circuit to the timer motor 137 is made through conductors 138,blade 135, terminal 136, conductors 139, 140, motor 137, and conductors141, 132. A shunt circuit also is made through conductor 142, blowermotor 58, and conductors 143, 133, and 132. Thus, the blower motor willnow continue to run until the blade 135 is shifted into contact withterminal 144 and regardless of the shifting of blade 130 which controlsthe upper heater in the casting pot.

As a significant feature, when the blower motor is energized air isdirected through the nozzle 55 (FIG. 2) against the central bottomportion of pot 52 and the cooling and subsequent selectively controlledcrystallization of the hotmelt as it solidifies will take placeprogressively from the center of the female die 83 in an outwarddirection, from the embedded male die, and at the same time such coolingprogressively takes place in an upward direction since the lower heaters59, 60 of the casting pot are deenergized and the upper heaters 63, 64thereof are now producing heat. Contraction of the female die 83 towardthe emplaced male die 82 thus occurs while a reservoir of molten melt isstill present above the die plate 75 serving to compensate for shrinkageof the cooling lower portion of that female die. As will be understood,the molten metal above plate 75 is free to pass through thesymmetrically spaced apertures 76.

In general, this formation of the female die can be completed in aboutthirty minutes at which time the intemal cams of the timer cause bladeto shift into contact with terminal 145 meanwhile leaving blade incontact with terminal 136 and permitting the blower motor to continuerunning. When blade 130 is so shifted the circuit to the upper heaters63, 64 of the casting pot is interrupted and that pot and its contentsare then permitted to cool to a suitable handling temperature, forexample about 200 F.

Thereafter, at the time selected by the operator the timer blade 135 isshifted again into contact with terminal 144 interrupting the circuit tothe timer motor 137 and establishing a circuit through light 146. Whenthis light appears, the operator then opens main switch 100 and removesthe pull bar 67, attached plate 70, cast female die 81, and embeddedmale die 80 from the casting pot.

These elements are then disassembled, any melt remaining as sprues 82,83 is removed, and the male die is forced from the female die. Due tothe difference in coefficient of expansion of the male and female diematerials this removal of the male die may include a sufficientreheating of the female die by any suitable means, not shown, to cause aslight expansion of the female die material prior to pushing the maledie therefrom. While this procedure is being followed, the apparatus maynow be in its preparatory heating stage for making the subsequent femaledie.

Having thus described the method of practicing the invention and thecombination of coordinated apparatus by means of which it may bepracticed, it will be understood that the invention may also be embodiedin other forms without departing from the scope of the appended claims.

What is claimed is:

1. Apparatus for casting female cutting dies comprising in combination,an open-top casting pot having a side wall and a bottom, a first heatingmeans at the lower portion of said wall and a second heating means at anupper portion of said wall, an upwardly removable die plate disposed insaid pot at the upper portion of said wall and holding a male dieserving as a reusable core between the plate and the bottom of said potand in contact therewith, said die plate having a plurality of cut awayportions at the periphery of the plate and through which a molten meltpoured upon the plate is directed into the pot in surrounding relationto said male die core, motor driven blower means for directing a streamof cooling air against the bottom of the pot and to cause said melt tosolidify progressively outwardly from said male die core toward the wallof said pot, means for actuating each of said heating means prior topouring said melt into said pot and for thereafter deactivating at leastsaid first heating means, and means for activating said second heatingmeans for a predetermined period of time following the pouring of saidmelt thereby to cause said melt to solidify progressively upward in saidpot.

2. Apparatus as defined in claim 1 wherein said means for activatingsaid second heating means includes an electrical circuit having a timerserving to deactivate said second heating means upon expiration of saidperiod of time.

3. Apparatus as defined in claim 2 wherein said timer serves todeactivate said second heating means prior to the interruption of saidstream of air.

1. Apparatus for casting female cutting dies comprising in combination,an open-top casting pot having a side wall and a bottom, a first heatingmeans at the lower portion of said wall and a second heating means at anupper portion of said wall, an upwardly removable die plate disposed insaid pot at the upper portion of said wall and holding a male dieserving as a reusable core between the plate and the bottom of said potand in contact therewith, said die plate having a plurality of cut awayportions at the periphery of the plate and through which a molten meltpoured upon the plate is directed into the pot in surrounding relationto said male die core, motor driven blower means for directing a streamof cooling air against the bottom of the pot and to cause said melt tosolidify progressively outwardly from said male die core toward the wallof said pot, means for actuating each of said heating means prior topouring said melt into said pot and for thereafter deactivating at leastsaid first heating means, and means for activating said second heatingmeans for a predetermined period of time following the pouring of saidmelt thereby to cause said melt to solidify progressively upward in saidpot.
 2. Apparatus as defined in claim 1 wherein said means foractivating said second heating means includes an electrical circuithaving a timer serving to deactivate said second heating means uponexpiration of said period of time.
 3. Apparatus as defined in claim 2wherein said timer serves to deactivate said second heating means priorto the interruption of said stream of air.